The present invention generally relates to an information processing technique, and more specifically relates to a technique for improving accuracy in reading invisible information printed together with visible information on a medium such as paper.
With wide spread of an editing and publishing method for newspapers and magazines by using a computer, such as desk top publishing (DTP), there has been built business for providing PCs, PDAs, dedicated instruments and mobile phones via the Internet with pay contents stored in servers as digitalized original contents of articles and photos printed in the newspapers and magazines.
However, paper is still used as a main medium because of its information volume and convenience. For this reason, people in publishing business desire to utilize unused data stored in servers for business by combining paper media and digital contents in some way.
Japanese Patent Application Laid-open Publication No. 2006-229894 (the laid-open date is 31 Aug. 2006) discloses an “ELECTRONIC SCRAP SYSTEM” invented as a method for combining digital contents with printed materials of physical media such as paper, plastics and cloths. In this system, information related to the content of a conventional printed material is additionally printed as a usually-invisible two-dimensional barcode on the conventional printed material, with a transparent stealth ink (that is an invisible ink fluorescing by reacting to usually-invisible light, for example, ultraviolet rays or infrared rays, or absorbing these kinds of light). Then, in this system, this information and its related information are displayed and used together with the usual visible image by using a mobile phone equipped with a digital camera supporting the electric scrap system. The application discloses the basic method for providing various services by combining this information with original digital contents stored in a server.
With this method, a hybrid book giving a new added value to a usual printed material can be published by embedding invisible information on any place in texts, photos, illustrations and the like without taking care of an appearance and layout of visible information on the printed material.
When stealth information is printed on a printed material, the stealth information can be read without any problem on a good condition like a case where background visible information is uniform. However, when an invisible two-dimensional barcode is laid out on printed texts, a photo or illustration, the background inevitably makes an adverse affect on reading performance of the two-dimensional barcode. As a result, in an extreme case, the condition of a place where the barcode is laid out is so bad that the barcode cannot be read at all. In addition, in some cases, it may be necessary to take into consideration conditions of a printing medium, such as quality of paper and stain, and conditions of reading the printing medium, such as a case where the printing medium is folded and a place where the printing medium is read. For example, since printing media such as a newspaper are generally folded into two or four, it is preferable to lay out invisible information away from a place which is highly likely to be folded as mentioned above.
As an attempt for solving such problems, Japanese Patent Application No. 2005-195338 (International Patent Application No. PCT/JP2006/313058) provides the invention, “INVISIBLE CODE PRINTING SUPPORT SYSTEM.” This system aims to achieve a reading rate of 100% in a logical manner. Specifically, in order to lay out an invisible two-dimensional barcode for “the electronic scrap system” on a printed material, a DTP system in this system makes a simulation using an invisible barcode extraction algorithm, when the layout of the printed material is composed, for example. The DTP system carries out the simulation while checking whether or not a combination of background information and the invisible information to be laid out is appropriate for reading performance of an instrument supporting “the electronic scrap system. Thereby, the DTP system specifies or optimizes the color, the position, the size and the like of the invisible information to be laid out.
Use of this system not only makes it easier to create a printed material providing higher reading accuracy to the electronic scrap system. But also, when printed materials are produced, the use makes it possible to fully ensure that all the printed materials can provide such a function, not by performing 100% inspection but only by performing random inspection.
Here, in order to enhance reading accuracy, it is important to input, as parameters for simulation, closest possible values to actual conditions. Examples of the parameters include data on characteristics of inks and paper to be used for printing background and an invisible barcode, and data on an environment at a time when an instrument supporting the electronic scrap system extracts the invisible barcode. However, as for the invisible code printing support system (Japanese Patent Application No. 2005-195338, International Patent Application No. PCT/JP2006/313058), a specific method for finding values for parameters is not presented.